This invention relates generally to electrical stimulators and more particularly to implantable cardioverters and defibrillators.
Implantable stimulator, including pacemakers, cardioverters and defibrillators have been proposed which employ multi-electrode systems for sensing cardiac signals and delivery of pacing, cardioversion or defibrillation pulses. Switching between various electrode configurations in order to optimize the therapy being delivered has often been suggested. For example, U.S. Pat. No. 4,958,632, issued to Duggan et al. discloses an early microprocessor controlled pacemaker provided with switching circuitry which allows the device to be operated in unipolar or bipolar mode. Similarly, in the context of implantable cardioverters and defibrillators, internal switching circuitry for allowing selection of particular electrode configurations out of three or more available electrodes have been widely disclosed. For example, U.S. Pat. No. 5,129,394, issued to Mehra discloses such a system.
It has also been proposed to employ a switch located in a connector block to switch between unipolar and bipolar electrode configurations in the context of cardiac pacing, as disclosed in U.S. Pat. No. 4,301,805 issued to Peers Trevarton et al or to employ a switch located in or on the lead body to switch between multiple electrodes in the context of a defibrillation lead, as disclosed in allowed U.S. patent application Ser. No. 07/621,112, filed Nov. 30, 1990 by Pohndorf et al.
In use of clinically available implantable defibrillators which provide for use of three or more defibrillation electrodes, it is not always the practice to implant such devices with all available leads present. In some cases, the physician may desire to implant only two of three available leads, leaving one connector bore within the connector assembly of the device unfilled. In the context of the Medtronic Model 7216 and 7217 implantable pacemaker/cardioverter/defibrillators, a plug is provided to fill the unused connector bore, to prevent fluid ingress.